The research focuses on the central unsolved problem of psychiatric epidemiology, the problem of how to measure psychiatric disorders independently of treatment status in the general population. Its major aim is to test the sensitivity and specificity of the newly developed Psychiatric Epidemiology Research Interview (PERI) as a first-stage instrument to screen functional p;sychiatric disorders among adults in a demographically complex urban population. To this end, two field operations would be conducted. In the first, we will investigate PERI's relationship to other potential screening instruments on a sample of 600 adults from the general population and calibrate PERI on a sample of 500 psychiatric patients with diagnoses of schizophrenia, affective disorder, neurotic types of disorder other than affective, anti-social personality, and addictions to drugs and alcohol. In the second, we would examine PERI's relationship to two diagnostic instruments the Present State Examination (PSE) and the Schedule for Affective Disorders and Schizophrenia (SADS). In this second study, interviews would be conducted with a full probability sample of 1400 adults from the general population. The research setting for these investigations is Washington Heights, a section of Manhattan in New York City that surrounds the Columbia Presbyterian Medical Center. It is a demographically complex urban area containing large percentages of blacks and Puerto Ricans as well as members of more advantaged ethinic groups. The results should provide a textbook example of the development and testing of a two-stage procedure for case identification and classification. This funded methodological research complements less fully described substantive investigations for which funds will be sought.